Condensed Matter > Quantum Gases

Title:
Shock Waves in a Superfluid with Higher-Order Dispersion

Abstract: Higher-order dispersion can lead to intriguing dynamics that are becoming a
focus of modern hydrodynamics research. Such systems occur naturally, for
example in shallow water waves and nonlinear optics, for which several types of
novel dispersive shocks structures have been identified. Here we introduce
ultracold atoms as a tunable quantum simulations platform for higher-order
systems. Degenerate quantum gases are well controlled model systems for the
experimental study of dispersive hydrodynamics in superfluids and have been
used to investigate phenomena such as vortices, solitons, dispersive shock
waves and quantum turbulence. With the advent of Raman-induced spin-orbit
coupling, the dispersion of a dilute gas Bose-Einstein condensate can be
modified in a flexible way, allowing for detailed investigations of
higher-order dispersion dynamics. Here we present a combined experimental and
theoretical study of shock structures generated in such a system. The breaking
of Galilean invariance by the spin-orbit coupling allows two different types of
shock structures to emerge simultaneously in a single system. Numerical
simulations suggest that the behavior of these shock structures is affected by
interactions with vortices in a manner reminiscent of emerging viscous
hydrodynamics due to an underlying quantum turbulence in the system. This
result suggests that spin-orbit coupling can be used as a powerful means to tun
the effective viscosity in cold-atom experiments serving as quantum simulators
of turbulent hydrodynamics, with applications from condensed matter and optics
to quantum simulations of neutron stars.